A dual-mode band-pass filter (BPF) for the fifth generation (5G) N78 band applications is proposed based on a 2-layer low temperature cofired ceramic (LTCC) substrate. The proposed BPF is built with a square resonator and two pairs of open-stubs, which suppressed the 2nd-order and 3rd-order 27 and 21 dB, respectively. The proposed BPF not only achieved a size reduction of 50% compared with a single-mode implementation, but also possessed a non-orthogonal input/output (I/O) feeding style, which presents convenient interconnection and integration with neighboring devices. Moreover, the dual-mode BPF does not need a conventional disturbing element to excite two degenerate modes. Comparison and discussion are carried out as well.
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